It's not just Lisp, but it includes pilog, a built-in Prolog, a database and coroutines. PicoLisp is an amazing piece of work by essentially one man, and has been used in real-world database applications since the late 1980s. They were trying to build hardware to run it, hence PilMCU, but too much inertia has lead now to PilOS. Yeah, PilOS!

Now to get Shen running on PicoLisp after Alex adds networking!